Rat cognitive function during and after treatment with the cannabinoid agonist, HU 210

To ascertain whether the cannabinoidagonist HU 210 (25, 50, or 100mg/kg, IP) influences rat spatial learning, water-maze performance was examined in theplace (hidden platform)—and cue (visible platform)—versions of the Morris water maze. In addition, other unlearned behaviorswere examined, namely, vocalization and wall hugging during the place task, and motor abilities during a motor test battery.The results obtained show that HU 210 at 50 or 100mg/kg (once daily for 4 days, 60 min before a daily session) impairedlearning in the place version but not in the cue one; wall hugging and enhanced vocalization were also displayed by the animalsin the fourth session. Motor activity was compromised by the same treatment schedule. When the drug was discontinued,the effects produced by HU 210 at 50mg/kg reversed in 3 days, while disruption of acquisition and vocalization caused byHU 210 at 100mg/kg remained after 7 days’ abstinence. Discussion centers on the possible specific cognitive mechanisms affectedby the drug and on aspecific factors (i.e., anxiety-like state), which may contribute to the impairment of spatial learning.